Can nutrition affect chemical toxicity?

Universally, the general population is exposed to a variety of "toxic" substances. Some of these are from manufactured goods and some from air and water pollution. Toxins are also normally found in many foods; however, unless the exposure is overwhelming, we are many times (even unknowingly) protected by the foods we eat. A judicious choice of food will counteract noxious agents. Therefore, the diet can be a major factor in determining who does and who does not show toxic symptoms following exposure. This review will cover three aspects. The first will be on protectors against metal toxicity. For example, whereas humans can consume fish that have absorbed mercury from contaminated bay water, selenium can act as a natural antagonist for mercury poisoning. (Naturally, too much selenium itself can be detrimental!) Some vegetables can accumulate cadmium from contaminated soil, and zinc from a variety of nuts is an antagonist of cadmium toxicity. Nitrites in preserved meats can be converted into nitroamines by saliva or mild stomach acid. Vitamin C found in oranges and bell peppers can inhibit that conversion. In addition, calcium antagonizes both lead and aluminum toxicity. The second aspect is on oxidants and antioxidants. Oxidative stress can lead to some cancers, atherosclerosis, and adverse effects of aging. Antioxidants are the best protectors of the damage caused by reactive oxygen species (ROS). The most effective antioxidants are found in highly colored fruits and vegetables such as carrots, tomatoes, and berries, called carotenoids. Flavonoids (polyphenols), another class of effective antioxidants that negate ROS, may or may not be colored. The third aspect is on gaps in current knowledge. Many foods naturally contain chemicals that are, in larger concentrations, quite toxic or carcinogenic. Biotransformations (detoxification mechanisms) involving type I and type II enzymes are known. Some foods do modify these enzymes either positively or negatively. Grapefruit contains a substance that inhibits an isoform of P450, making some cardiac drugs, as substrates, more toxic. There is inadequate information on what specific components are in a variety of foods that are associated with cancer prevention. The experimental carcinogenic compound (and suspected as a human carcinogen) found in overcooked, burnt, and fried meats and fish, namely IQ (2-amino-3-methyl-3H-imidazo[4,5f]quinoline, will be used as a prototype for what needs to be known about foods that will affect toxins.